There has been widely used as a generator for an internal combustion engine a magneto generator which comprises a magneto rotor, which has a cylindrical flywheel and a magnet attached to an outer circumferential side of a peripheral wall portion of the flywheel, and a stator, which is constructed by winding a generating coil around a core having a magnetic pole portion opposed to the outer circumference of the peripheral wall portion of the flywheel and a magnetic pole of a permanent magnet via a predetermined gap.
In a magneto generator of this kind, in which a flywheel is made of a casting, as shown in the Japanese Patent Application Laid-Open No. 8-80020, a magneto rotor was constructed by attaching a magnet to a recessed portion formed in an outer circumference of a peripheral wall portion of the flywheel.
However, in a case where a flywheel made by the press forming of a steel sheet is used, because the sheet thickness of the peripheral wall portion of the flywheel is small, it was difficult to form, with good accuracy, a recessed portion having a depth capable of housing the magnet in the outer circumference of the peripheral wall portion in order to attach the magnet to the interior of the recessed portion.
Therefore, when a press formed flywheel is used, as described in the Japanese Patent Application Laid-Open No. 2001-95216, it is general practice to construct a magneto rotor by bonding one magnetic pole face of a magnet on an outer circumferential surface of a peripheral wall portion of the flywheel.
However, when a magnet is bonded to an outer circumferential surface of a peripheral wall portion of the flywheel, the magnet is protruded to the outside from the outer circumferential surface of the peripheral wall portion of the flywheel and, therefore, in assembling a magneto generator, the magnetic pole of the stator abuts against the magnet or a tool abuts against the magnet, which occurs the problem that the magnet is apt to be broken.
Furthermore, as disclosed in the Japanese Patent Application Laid-Open No. 2001-95216, in a case where a magnet is bonded to an outer circumference of a peripheral portion of the flywheel, there was a problem that it is not easy to position the magnet until an adhesive hardens.